1. Field of the Invention
The present invention relates to a sealing apparatus attached to an inner periphery of a boot, which is provided between an inner and an outer element of a universal joint of a propeller shaft and a drive shaft of a vehicle, for example, in order to seal and hold a lubricating agent such as grease therein, and to prevent dust, water or the like from invading from the outside.
2. Description of the Related Art
Conventionally, a universal joint for use in a drive shaft of a vehicle, as illustrated in FIG. 10, for example, includes a tripod type constant speed joint comprising a cylindrical outer and an inner element fitted into the outer element. In this universal joint xe2x80x98axe2x80x99, an inner element xe2x80x98bxe2x80x99 is provided with a drive shaft xe2x80x98dxe2x80x99, a ring shaped member mounted to an end of the drive shaft xe2x80x98dxe2x80x99, and three rollers turnably supported, respectively, by three bearings extending in a peripheral direction from the ring shaped member with equal intervals and outwardly in a radial direction. In addition, a three-stripe guide groove formed along an axial direction for housing the three rollers of the inner element xe2x80x98bxe2x80x99, respectively, is formed on an inner periphery of an outer element xe2x80x98cxe2x80x99. Further, a torque is transmitted between the inner element xe2x80x98bxe2x80x99 and the outer element xe2x80x98cxe2x80x99 via the three rollers engaged with the guide groove.
On the other hand, a boot xe2x80x98exe2x80x99 mounted across the outer element xe2x80x98cxe2x80x99 and the inner element xe2x80x98bxe2x80x99 of this universal joint xe2x80x98axe2x80x99 comprises a cylindrical adapter xe2x80x98fxe2x80x99 and an expandable flexible boot main body xe2x80x98gxe2x80x99 securely fixed to one end of the adapter xc2x0 F. The adapter xe2x80x98fxe2x80x99 is engaged with an outer periphery of the outer element xe2x80x98cxe2x80x99, and the boot main body xe2x80x98gxe2x80x99 is engaged with an outer periphery of the drive shaft xe2x80x98dxe2x80x99. Further, an O-ring xe2x80x98hxe2x80x99 is attached to an annular stepped portion formed on the inner periphery of the adapter xe2x80x98fxe2x80x99. In this manner, the boot xe2x80x98exe2x80x99 causes its inside to be held in an airtight manner, a lubricating agent filled therein is prevented from leaking, and dust, water or the like is prevented from invading into the inside.
In the meantime, in the prior art, the O-ring xe2x80x98hxe2x80x99 attached to the stepped portion of the inner periphery of the adapter xe2x80x98fxe2x80x99 is easily deformed because the shape holding force of the O-ring itself is small, which is caused by flexibility of its forming material. As illustrated if FIG. 11, even if a portion is at a normal position of the stepped portion, the other portion is sometimes attached in a state in which it is displaced from the normal portion. If the inner element xe2x80x98bxe2x80x99 and the outer element xe2x80x98cxe2x80x99 are assembled with each other in such state, the O-ring xe2x80x98hxe2x80x99 is geared between surfaces other than a sealing surface of the outer element xe2x80x98cxe2x80x99, and sufficient sealing capability cannot be performed.
In addition, in such state, the O-ring xe2x80x98hxe2x80x99 easily slips off from the stepped portion Further, in order to prevent the O-ring from deforming when the O-ring xe2x80x98hxe2x80x99 is attached to the stepped portion of the adapter xe2x80x98fxe2x80x99, it is difficult to hold the O-ring xe2x80x98hxe2x80x99 with large elastic force in a radial direction on the inner periphery of the adapter xe2x80x98fxe2x80x99. Thus, the holding force of the O-ring xe2x80x98hxe2x80x99 to the adapter xe2x80x98fxe2x80x99 is small. As a result, even if the O-ring xe2x80x98hxe2x80x99 is attached to a normal position, in the case where a shock is applied to the boot xe2x80x98exe2x80x99, the O-ring xe2x80x98hxe2x80x99 sometimes slips off from the stepped portion. Thus, the inner element xe2x80x98bxe2x80x99 and the outer element xe2x80x98cxe2x80x99 are assembled with each other while the O-ring xe2x80x98hxe2x80x99 slips off, and the sealing capability will be degraded.
Therefore, assembling work must be performed while it is checked whether or not the O-ring xe2x80x98hxe2x80x99 is properly attached to the adapter xe2x80x98fxe2x80x99, which has lowered the efficiency of the assembly of the universal joint xe2x80x98axe2x80x99.
The present invention has been achieved in view of such circumference. It is an object of the present invention to provide a sealing apparatus securely held on an inner periphery of a cylindrical member in a normal state, thereby improving the efficiency of assembly of a member to which the sealing apparatus is attached.
In accordance with the present application, there is provided a sealing apparatus comprising: an elastic member having a sealing portion coming into contact with a sealing surface of a cylindrical member in an airtight manner, and a reinforcing member having the elastic member securely fixed thereto, the sealing apparatus being attached to an inner periphery of the cylindrical member having a stepped portion formed between a small cylinder portion having a predetermined inner diameter and a large cylinder portion having an inner diameter larger than the small cylinder portion, wherein the sealing surface is formed on at least one of an inner surface of the stepped portion and an inner periphery surface of the large cylinder portion, and further, a holding portion press-inserted into the inner periphery of the small cylinder portion is provided so as to hold the reinforcing member on the inner periphery of the cylindrical member.
In this specification, circles such as cylinder, ring, circumference, arc or the like include a substantially circular shape that is a shape close to a circle as well as an exact circular shape. In addition, in the specification, an outer engagement completion close position means a position at which, even if a communication passage is closed at the position, and then, the outer element is relatively moved to an engagement completion position relevant to a boot, the boot does not inflate along with a rise of the air pressure inside of the boot caused by the relative movement, or even if such inflation occurs, the inflation is so slight that it can be substantially ignored.